Vascular diseases such as thrombus and embolism are pathophysiologically initiated by platelet activation firstly. Therefore, antiplatelet therapy is crucial for the prevention of vascular diseases. ADP (adenosine diphosphate) is an important pathologic and physiologic platelet agonist. When a blood vessel is damaged, ADP is released from damaged cells and activated platelets to the blood, and then acts on other platelets. ADP receptor antagonists inhibit the attachment between the fibrinogen and the platelet membrane GPIIb/IIIa, activate platelet adenylate cyclase, and increase cAMP (cyclic adenosine monophosphate) level in platelets and thereby inhibit platelets mainly by inhibiting platelet membrane ADP receptor expression, binding and activity.
Prasugrel (formula I), a new generation of ADP receptor antagonist, is a novel prodrug-type antiplatelet drug (CN1074446A). For ADP-induced platelet aggregation in rats, oral administration of prasugrel is ten times more potent than that of ADP receptor antagonist, clopidogrel, which is available from the market.

The plasma concentration of active metabolites of prasugrel is ten times higher than that of clopidogrel as well, indicating that the greater efficacy of prasugrel may result from its faster metabolic rate.
CN1452624A discloses prasugrel hydrochloride and maleate, which exhibit good activity in oral absorption, metabolization, and inhibition of platelet aggregation and weak toxicity.
CN101255169A discloses prasugrel hydrobromate, which exhibits improved water solubility and thermal stability as compared to hydrochloride, and unsatisfactory performance in high humidity and light stability. However, for pharmaceutical compounds, stability is one of important features thereof, and good stability often has a beneficial effect on industrial processes including preparation, storage, usage (manufacturing raw material into formulation) and the like.